The present invention relates to drive devices having torsional vibration dampers.
More particularly, the present invention relates to devices for driving at least one piece of equipment, from a driving shaft, having a torsional vibration damper for rotating masses, which devices comprise a primary element intended to be fixed to the driving shaft and a secondary element intended to be connected to the said at least one piece of equipment, the said primary element being linked, on the one hand, to an inertia ring via first elastic means and, on the other hand, to the secondary element via second elastic means.
Such drive devices are well known; they are, for example, mounted at the end of the driving shaft of a motor vehicle and permit the rotational driving of one or (more) piece(s) of equipment, such as an alternator, a fan or another piece of equipment. A device of this kind is described, for example, in the document DE-A-4322710.
Such a drive device is provided so that two main functions are fulfilled, namely a damping function and a filtering function.
The damping function dampens the torsional vibrations of the driving shaft, for example the crankshaft of the engine of the vehicle, thanks to the association of the inertia ring and the first elastic means, the properties of which, inertia and elasticity, are determined as a function of the dynamic characteristics of the driving shaft and the moving equipment linked to it.
The filtering function filters the cyclic irregularities of the driving shaft; in the case of a motor-vehicle engine, it is known that these irregularities appear at low speed and that they impair the correct operation of the engine and the mechanical stability of the pieces of equipment driven by the device; this filtering function is fulfilled by the second elastic means which are chosen to have great torsional flexibility, which is calculated while taking into account the pieces of equipment driven by the device.
Such drive devices work well but, as indicated, their structure and therefore their space requirement is dependent, on the one hand, on the driving component, and even [sic] the driving shaft and the moving equipment linked to it, and, on the other hand, on the piece(s) of equipment which is (or are) driven; it is not always possible therefore, for a given application, to dimension them strictly in accordance with the calculations, which therefore impairs the efficiency and the mechanical stability of the components concerned.
The object of the present invention is to overcome these disadvantages and its subject is a drive device which can be adapted rigorously, whatever the application.